Self-cleaning SERS sensor based on flexible Ni₃S₂/MoS₂@Ag@PDMS composites for label-free multiplex volatile organic compounds detection

Flexible self-cleaning surface-enhanced Raman scattering (SERS) sensors are highly desirable for the detection of various environmental pollutants, including volatile organic compounds (VOCs). However, achieving sensitive detection without labeling and ensuring efficient cyclic use remain significant challenges. Herein, we introduce a direct approach to create a versatile Ni₃S₂/MoS₂@Ag@PDMS (PDMS = polydimethylsiloxane) composite SERS substrate using chemical vapor deposition technology. The produced substrate shows outstanding performance, offering extremely low detection sensitivity (1.0 × 10⁻¹² M 4-aminobenzenethiol) and high enhancement factors (approximately 10⁷). The interactions between the rod-shaped Ni₃S₂/MoS₂@Ag heterostructure and the molecules facilitate the transfer of charge, resulting in an increased electric field enhancement of the exciton resonance. This has the dual benefit of providing a self-cleaning effect and enhancing SERS efficiency. Importantly, the substrate enables sensitive detection of VOCs gas molecules without the need for labels, achieving a minimum detectable concentration as low as 1 ppm for o-dichlorobenzene, due to the preconcentration effect of PDMS. Theoretical calculations further explain the combined effect of electromagnetic and chemical enhancement in this composite substrate. By utilizing the developed visual SERS barcode, quick multiple detection and analysis of mixtures can be accomplished. This flexible and versatile SERS technique has significant potential for on-site detection and analysis of environmental pollutants, opening the doors for the development of a wearable in-situ SERS sensing platform.